Fig. 1494.

The gauge known as the American Standard Wire-Gauge was designed by Messrs. Brown and Sharpe to correct the discrepancies of the old Birmingham wire-gauge by establishing a regular proportion of the thirty-nine successive steps between the 0000 and 36 gauge-number of that gauge. In the American Standard (which is also called the Brown and Sharpe gauge) the value of 0.46 or 46⁄100 has been taken as that for 0000 or the largest dimension of the gauge. Then by successive and uniform decrements, each number following being obtained from multiplying its predecessor by 0.890522 (which is the same thing as deducting 10.9478 per cent.), the final value for number 36 is reached at 0.005, which corresponds with number 35 of the Birmingham wire-gauge. The principle of the gauge is shown in [Fig. 1495], which represents a gauge for jewelers, having an angular aperture with the gauge-numbers marked on the edge, the lines and numbers being equidistant.

Fig. 1495.

The advantage of this system is that the instrument is easy to produce, the difference between any two gauge-numbers being easily found by calculation; and the gauge is easy to originate, since the opening, being of the proper width at the open end, the sides terminating at the proper distance and being made straight, the intermediate gauge-sizes may be accurately marked by the necessary number of equidistant lines.

Wire, to be measured by such a gauge, is simply inserted into and passed up the aperture until it meets the sides of the same, which gives the advantage that the size of the wire may be obtained, even though its diameter vary from a gauge-number. This could not be done with a gauge in which each gauge-number and size is given in a separate aperture or notch. A comparison between the Brown and Sharpe and the Birmingham wire-gauge is shown in [Fig. 1494], in which a piece of wire is inserted, showing that No. 15 by the Birmingham gauge is No. 13 by the Brown and Sharpe gauge.

The gauge-numbers and sizes of the same in decimal parts of an inch, of the American standard or Brown and Sharpe gauge, are given in the table following:—

No. of
Wire-
Gauge.		American or New Standard.No. of
Wire-
Gauge.		American or New Standard.
Size of each
number in
decimal
parts of
an inch.		Difference
between
consecutive
numbers in
decimal parts
of an inch.		Size of each
number in
decimal
parts of
an inch.		Difference
between
consecutive
numbers in
decimal parts
of an inch.
0000.460——19.03589.00441
000.40964.0503620.03196.00393
00.36480.0448421.02846.00350
0.32495.0399422.02535.00311
1.28930.0355623.02257.00278
2.25763.0316724.0201.00247
3.22942.0282125.0179.00220
4.20431.0251126.01594.00196
5.18194.0223727.01419.00174
6.16202.0199228.01264.00155
7.14428.0177429.01126.00138
8.12849.0157930.01002.00123
9.11443.0140631.00893.00110
10.10189.0125432.00795.00098
11.09074.0110533.00708.00087
12.08081.0099334.0063.00078
13.07196.0088535.00561.00069
14.06408.0078836.005.00061
15.05707.0070237.00445.00055
16.05082.0062538.00396.00049
17.04525.0055639.00353.00043
18.0403.0049540.00314.00039

This gauge is now the standard by which rolled sheet brass and seamless brass tubing is made in the United States. It is also sometimes used as a gauge for the copper wire used for electrical purposes, being termed the American Standard; but unless the words “American Standard” are employed, the above wire is supplied by the Birmingham wire-gauge numbers. The brass wire manufacturers have not yet adopted the Brown and Sharpe gauge; hence, for brass wire the Birmingham gauge is the standard.